Portfolio ↗

DNS

Resolution, TTL behaviour, traffic steering and failover latency.

5Questions
7Flashcards
3Terms
Drill this topic All of Networking
Questions

5 to work through

  1. beginner Multiple choice

    At 09:00 a team creates the DNS record for a new regional endpoint. It resolves from their laptops at once, but part of the fleet keeps getting NXDOMAIN until about 09:20 even though the record's TTL is 60 seconds. Why?

    2 min answer
  2. intermediate Multiple choice

    Why is DNS a poor primary mechanism for fast failover, and what should be used instead for a globally distributed service?

    2 min answer
  3. intermediate

    You use DNS with a 60-second TTL for regional failover. During a test, some traffic still hit the failed region 40 minutes later. Explain.

    2 min answer
  4. advanced

    A globally distributed API experiences a regional networking failure. How should DNS, health checks, traffic steering, connection draining, failover and consistency interact?

    2 min answer
  5. advanced

    Your DR plan assumes a 60-second DNS TTL gives 60-second failover. Traffic to the failed region continues for 20 minutes. Explain and design something better.

    2 min answer
Terminology

3 terms in this topic

concept

DNS Resolution Chain

The sequence of lookups from browser cache through OS cache, recursive resolver, root, TLD and authoritative server that turns a name into an address.

 concept

DNS TTL

The time a DNS record may be cached, and a value that resolvers, operating systems and applications honour inconsistently.

 practice

DNS TTL Strategy

Choosing record lifetimes to balance failover speed against query volume, knowing that resolvers and clients do not reliably honour them.
Networking

Neighbouring topics

Networking

General material on the network path underneath an architecture.

4 quiz 13 cards 14 terms

TCP/IP

Handshakes, congestion control, head-of-line blocking and connection reuse.

3 quiz 9 cards 2 terms

HTTP/1.1, HTTP/2 & HTTP/3

Multiplexing, prioritisation and the transport each is built on.

4 quiz 11 cards 5 terms

TLS & Certificates

Encryption, integrity, authentication, termination points and expiry.

6 quiz 7 cards 5 terms

Layer 4 vs Layer 7

Connection-level versus request-level balancing, and what each unlocks.

4 quiz 10 cards 3 terms

Reverse Proxies

One place for TLS, routing, caching, compression and rate limiting.

3 quiz 9 cards 5 terms

Content Delivery Networks

Edge caching, origin offload, spike absorption and dynamic content.

8 quiz 11 cards 6 terms

Firewalls & Security Groups

Default-deny, stateful rules, and restricting egress as well as ingress.

5 quiz 8 cards 3 terms

NAT & Egress

Outbound-only connectivity, its per-gigabyte cost and its zone binding.

4 quiz 11 cards 4 terms

VPC Design

Address planning, peering and the ranges you can never resize.

3 quiz 9 cards 3 terms

Subnetting

Tiering, zone binding, and sizing for an address-hungry platform.

3 quiz 9 cards 3 terms

Routing & BGP

How traffic finds you, anycast, and route withdrawal as a failure mode.

2 quiz 8 cards 5 terms

Service Mesh Networking

Sidecar proxies supplying mTLS, retries and traffic policy.

4 quiz 11 cards 3 terms

WebSockets & Realtime

Persistent bidirectional connections and the capacity model they impose.

6 quiz 13 cards 6 terms

gRPC Transport

HTTP/2 multiplexing, binary encoding and streaming semantics.

4 quiz 12 cards 3 terms

API Gateways

The single entry point, and the business logic that must stay out of it.

3 quiz 10 cards 4 terms

Network Performance

Latency floors, bandwidth-delay product, and what no code change fixes.

5 quiz 13 cards 5 terms

Private Connectivity

Private endpoints, peering and dedicated links to managed services.

4 quiz 7 cards 3 terms

Network Troubleshooting

Flow logs, packet paths, and localising a problem to a hop.

6 quiz 8 cards 3 terms